Typically, wind generators are classified based on their size and generation capacity. The large wind generators present rotor diameters in excess of 45 meters and generating capacities in excess to 1 MW; medium wind generators have diameters between 12 and 45 meters and generate between 40 and 999 kW; small wind generators have diameters between 3 and 12 meters and produce between 2 and 40 kW; and finally, micro wind generators have diameters smaller than 3 meters and power generation capacities not surpassing 2 kW.
Although the use of large and medium sized systems have been more extensively used worldwide, in order for these to operate adequately, high speed wind conditions are necessary, and a stable wind direction is preferable.
Worldwide, the vast majority of power generated from wind energy installed is obtained from great power systems, reaching extremes such as a nominal capacity system of power generation in excess of 6 MW, known as Enercom E-126.
In general, all usage systems primarily are in the 2 MW range per system, such as the V80-2.0 MW turbine manufactured by Vestas (Vestas Wind Systems A/S, 2009-1). Unfortunately, the great majority of these systems require wind conditions far in excess to those conditions which could be obtained in urban zones worldwide or zones close to the equator and mountainous regions. The limitation is such for these systems for wind conditions such as those in equatorial countries that the wind turbine offered by Vestas for low wind potential, the V100-1.8 MW (Vestas Wind Systems A/S, 2009-2), has an input speed (Cut in wind speed) of 4 m/s, for which it generates total power under 200 kW, despite its spanning area is in excess of 7800 m2.
Amongst the vertical axis wind generators, amongst several, two types stand out; the Savonius-type wind generators, which operate under a differential drag principle between the two faces of each vane, and the Darrieus-type wind generators, which have aerodynamic profiles that provide rotational torque through lift forces. The Savonius-type wind generators are ideal for use in low wind speed conditions or startup moments; however, the Savonius-type wind generators have the problem of being poorly efficient. The Darrieus-type wind generators require greater speeds and present greater efficiencies, thus limiting their use to certain countries and determined geographical zones.
For low powers, the available commercial offer is significantly reduced. For example, Enercom, one of the top worldwide wind generator manufacturers, produces a turbine having power output of 330 kW and 876 m2 as its smallest in its portfolio, known as E-33, while Vestas has developed its V52-850 kW (Vestas Wind Systems A/S, 2009-3) with power generation under 100 kW for wind speeds not exceeding 5 m/s (Cut in wind speed 4 m/s) in a 52 m diameter.
Therefore, one of the greatest problems surfacing with power generation from clean energies, particularly wind energy, is that a great amount of wind is required in order to carry out optimal power production. Likewise, in order to achieve movement of the devices in charge of energy conversion, it is currently required that the same have gigantic sizes, in order for a small movement to be converted in some electrical energy.
Thus, a plurality of disclosures exists in the art related to wind generators or electric power generation systems generated from wind energy. Among this group WO 2009/092867 is found, which discloses a wind generator having a rotor formed by one unit that includes a support unit clamped to a second support unit. The second support unit rotates about the first unit around the vertical axis of the wind generator. In this device, the units forming the blades are fixed to another support unit and an electric generator stator is also held by the support units. The blades form units including a combination of Savonius-type blades and a Darrieus-type assembly with a relatively fixed position. The wind generator produces electrical energy for an external lighting system on streets and avenues. The Darrieus-type turbine blades have a National Advisory Committee for Aeronautics (NACA 015)-type profile.
However, the wind generator claimed in said document shows the disadvantage of requiring that wind direction must be in a specific direction in order to initiate blade movement, something that is not practical in every season and in all countries, primarily those countries close to the equator where wind generation is very little and wind direction varies constantly. Hence, a design is needed where the wind generator blades are moved with very little wind energy and initiate their movement with winds coming from different directions.
On the other hand, GB 2404227 discloses a turbine having an axis that rotates about a longitudinal axis having long-shaped blades resembling a troposkein. The structure's ends compensate from the axis in such a manner the blades are helical and the section perpendicular to the axis is aerodynamic. The section has a defined edge between the interior and exterior edges next to the radius from the axis. The turbine has improved characteristics enabling it to work efficiently at high wind speeds. Optionally, the blades may have a foam core and a coating made of composite material.
Although the above wind generator improves efficacy at low wind speeds, said apparatus has only one blade design system, whereby it may be asserted it works at relatively high wind speeds, but does not work with low speeds, i.e., it is limited for installation solely in geographical areas with relatively high wind speeds, but does not work when there are mixed wind speeds and thus, requires a large wind current to initiate movement and begin to generate electrical energy.
Furthermore, GB 2451670 refers to a wind generator comprising a rotor having a rotation axis that is transverse to wind flow direction. The rotor has multiple blades arranged about the rotation axis. Each blade has an aerodynamic profile formed in such a way the profile of each blade is positioned at an angle between 0° and 90° from a perpendicular plane to the rotation axis. The turbine may be defined as a modified Darrieus rotor having improved performance due to the rib-shaped or concave shape of the blades having reduced drag and greater energy production efficiency.
As with the above document, the invention described herein does not have an internal blade system that increases energy generation efficiency at low wind speeds. This limits its range of use and where the generator may be installed, considering it requires installation in geographical zones exhibiting high wind speeds.
Another prior art document related to the technology of the instant invention is international application WO 2008/157174, which discloses a wind generator showing a group of long blades having a long core with a crossed profile defining a curved cross section at one end having a radius, a linear intermediate cross section tangent to the curved cross section and a curved intermediate cross section having a lesser radius in comparison to the exterior curved cross section radius. The long core is accompanied by a second core also being long-shaped which between both, define a helix. In this wind generator, the cross section profile is maintained constant through the long core, the wind turbine is a Savonius-type turbine and the helix shape shown maintains a soft rotation that does not transmit vibration to the turbine components.
Different to the above generators, the invention reported in WO 2008/157174 refers to an effective system when low wind speeds are present, but does not have good power generation when facing high speeds and the device turns inoperative, thus being poorly efficient in certain geographical areas.
Finally, JP 2007092599 discloses a composite turbine having a pair of Savonius-type blades installed in the generator's wind incidence surface. This arrangement also has a pair of profile blades placed between the Savonius-type blades. The Savonius-type and profile-type blades are extended axially. The diameters of both blade types vary with respect to the cross section of the portion over which the wind hits. This double type blade arrangement has the advantage of being able to initiate rotation at low wind speeds efficiently converting movement into energy, showing greater efficiency at the rotation onset.
Considering the above information, it is evident there was a need in the art for designing and implementing a system for power generation from wind energy, having a double blade system allowing for optimal operation and improving the efficiency of the system both at low wind speeds as well as high wind speeds, in order to be able to be installed in any geographical zone, especially in countries close to the equator where winds are relatively scarce. Likewise, it is necessary for the system to allow for optimal operation and power generation even when wind direction varies constantly.